We have implemented a protocol toward the long term goal of expanding the indications for thrombolytic therapy for ischemic stroke. The study name is MR Witness: A Phase IIa Safety Study of Intravenous Thrombolysis with Alteplase in MRI-Selected Patients. The objectives of this study are to: 1) determine the safety of intravenous alteplase (tPA) in subjects with unwitnessed stroke onset, last known well less than 24 hours before, and MRI evidence of early stroke (less than 6 hours from onset), 2) validate novel MRI profiles to improve the sensitivity while maintaining high specificity for detecting subjects with acute stroke, and 3) explore the clinical efficacy of using imaging surrogates in subjects with unwitnessed stroke onset who are treated with thrombolysis. Eighty adult male and female subjects with acute ischemic stroke who present within 24 hours since the time they were last known well and are outside the standard tPA time window, but have an MRI suggestive of early stroke treatable with thrombolysis. This is an open-label, Phase IIa safety study to determine if it is safe to extend intravenous thrombolytic treatment to subjects who are evaluated within 24 hours from last known well and eligible to receive thrombolytic treatment within 4.5 hours from symptom discovery with the assistance of an MRI-based witness when no human witness of stroke onset is available. The study is designed to investigate the safety in using standard diagnostic MRI in selecting patients for thrombolytic therapy when the last known well time places the patient beyond the current IV thrombolytic time window. We will apply the following definition of treatable stroke as diffusion-positive, FLAIR-negative approach (DPFN) shown by us and several other centers to be indicative of early stage stroke. During the study course we will also consider comparable MRI models. A posttreatment safety evaluation using non-contrast CT will be performed for all treated subjects, consistent with standards of care after treatment with IV tPA. The maximum total number of subjects treat with tPA will be 80. A DSMB will independently monitor for safety, and stopping rules are defined to stop the study early if excessive symptomatic intracranial hemorrhage (sICH) rates occur. The stopping boundary for the trial is a hybrid of two conditions such that if an unacceptably high hemorrhage rate is detected by either condition, the trial will be terminated for safety concerns. The two conditions are the lower 95% confidence bound for the true hemorrhage rate is >5.3% or the absolute number of sICH exceeds 6. The primary outcome variable is sICH. Symptomatic hemorrhage is defined as any hemorrhage with neurological deterioration with an NIHSS score that increased by 4 or more points over baseline value or the lowest value in the first 7 days or any hemorrhage leading to death. The primary hypothesis is the rate of sICH will not exceed that observed in ECASS 3, a clinical trial that demonstrated the clinical efficacy of rt-PA up to 4.5 hours from last known well (5.3%, 95% exact Confidence Interval: 3.3% to 7.9%). Secondary outcomes will be clinical outcomes and other imaging features of ischemic stroke, e.g., brain edema, lesion volume growth. At 3 months from treatment, clinical outcome will be evaluated by modified Rankin Scale scores and compared to historical controls for both non-tPA and standard tPA treated patients. The clinical trial was designed and will be conducted in collaboration with colleagues from Massachusetts General Hospital in Boston. We are investigating the potential of interferon beta-1a to protect the blood brain barrier in acute ischemic stroke and prevent hemorrhagic complications of thrombolytic therapy. The first clinical trial in this series, Recombinant human interferon beta-1a in acute ischemic stroke: a dose escalation and safety study, completed enrollment this year. The purpose of this randomized double-blind placebo-controlled sequential dose escalation, phase 1 study is to investigate the safety of IFN-beta-1a in patients with acute ischemic stroke 3-24 hours from onset and to determine the maximum tolerated dose of administration in this setting. Five dose cohorts of 5 patients (4:1 active: placebo) at 11 mcg, 22 mcg, 44 mcg, 66 mcg and 88 mcg were planned. Patients receive interferon beta 1a or placebo once daily for 7 days (dose 1 is given intravenously; doses 2-7 are injected subcutaneously). Dose escalation is continuous unless drug-related toxicity reaches a predetermined level of one dose-limiting adverse event (1 of 4 treated) within a dose cohort, in which case a second cohort of 5 patients (4:1) will be treated at that dose. The study is to be terminated at a dose level at which 2 of 4 or 3 of 8 patients on active treatment have a severe dose limiting toxicity or when all planned dose cohorts are completed. This stopping rule was reached at the 44mcg dose. Blinded data verification and analysis, including pharmacokinetic and plasma MMP-9 concentrations, are ongoing. Upon unblinding, the results will be reviewed with the DSMB. Data analysis is on-going.